In photographic processing after exposure to light, silver halide photographic materials generally undergo a developing step, a desilvering step, a washing step and a drying step in succession. A color developer, a bleach-fix bath and a rinsing bath (and/or a stabilizing bath) used in individual processing steps are each replenished with a given amount of replenishing agent at every time when the processing quantity of photographic materials amounts to a predetermined value.
As to photographic waste solutions discharged as the quantity of silver halide photographic materials processed is increased, it has been strongly required in recent years from the viewpoint of environmental load to reduce the waste solution volume by adoption of replenishment rate-reduced processing and reclamation of spent processing solutions. As a medium for reduction of the waste solution volume, apparatus for concentrating waste solutions by reduced-pressure distillation is already in the actual use, and contributes to reduction in frequency of waste solution recovery and downsizing of storage space of waste solutions. However, as the apparatus consumes energy and does not aim to reuse waste solutions, it is difficult to say that the use of such apparatus is environmentally favorable. On the other hand, regeneration use of photographic waste solutions, especially regeneration use involving reduction in waste solution volume by concentration, requires a high-skill adjustment in ingredients of each processing solution. Therefore, the regeneration use is generally difficult to carry out in the so-called mini lab. And the regeneration use is performed almost exclusively in large-scale photofinishing laboratories (large lab) for not only the foregoing reason but also another reason that the large lab is a place large in processing quantity and favorable for management and activity maintenance of processing solutions, including waste solutions.
In mini lab, on the other hand, the processing quantity is small and waste solutions undergo deterioration with a lapse of time, so it is difficult to maintain the quality of waste solutions at a level enabling reuse thereof, and besides, there is a technical limit as mentioned above. Thus, the on-site regeneration processing as mentioned above cannot be performed. Such being the case, it is customary to store waste solutions and deliver over the stored ones to a waste solution recoverer to outsource the recovery processing. However, finding a space for storing waste solutions is required for the recovery processing to be outsourced, and it is further required to address laws and regulations governing the storage of specific industrial wastes.
With a recent trend toward widespread distribution of photofinishing laboratories, it has become an important challenge to find a convenient wastes-processing measure enabling solution of eco-friendliness problems in mini lab, especially to develop a convenient method for reusing waste solutions.
As an example of the method of reducing the volume of waste solutions by reduced-pressure distillation, mention may be made of the method disclosed in Patent Document 1 cited below, wherein processing waste solutions are solidified into powders and reused as solid processing chemicals. When a fixation waste solution is solidified into powder as it is and reused as a solid processing chemical, the fixation waste solution-originated silver ions cause an increase of silver ion concentration to result in inhibition on the desilvering of photosensitive materials. In such a reuse mode, therefore, silver ions are eliminated from the fixation waste solution by, e.g. electrolysis in advance of water removal, and then the resulting waste solution is solidified. This solidified matter is reused in its entirety, and regenerated as a solid processing chemical by supplementation with ingredients reduced by photographic processing.
However, the aforesaid mode requires an apparatus for eliminating silver ions, so a space to install the apparatus becomes necessary and thereby an increase in cost is caused. In addition, other chemical ingredients undergo degradation by oxidation during the elimination of silver ions, and it is impossible to solidify a small amount of waste solution without loss. Therefore, it cannot be said that the foregoing mode is a desirable mode.
In addition, electrolytic reduction of Ag ions gives rise to production of Ag2S and a decrease in bleaching activity with Fe(II) formation by simultaneous reduction of Fe(III) as a bleaching constituent. As a result, the running of rapid processing under use of the solid processing chemicals regenerated in the aforementioned mode creates new problems that cyan discoloration occurs, filters become clogged and stains are left on the sensitive materials processed.
Moreover, reduced-pressure distillation as a method for reducing the volume of waste solutions requires a vacuum pump for pressure reduction and, when excessive heat is applied to waste solutions during the distillation, there is a fear of evolution of decomposition gasses because a bleach-fix bath contains an ammonium salt and a sulfite. Thus, the application of reduced-pressure distillation as a measure against waste solutions in mini lab leaves problems in need of solution.
The following document is Patent Document 1 cited above as the background art relating to this invention.
Patent Document 1: JP-A-10-288829